Originally Posted by

**hencook**
Let's say I'm an astronaut standing on a platform in space. I push a ball, and the ball moves away from me at 10 mph. If a space shuttle was next to me at relative rest (we're both in orbit I guess), and I pushed the space shuttle with the same amount of force, would the shuttle push away from me at 10 mph as well?

John G has already answered qualitatively , but just to analyse what happens in terms of the mechanics of it, when you push with a certain force on the ball or shuttle, you push yourself with the same force in the opposite direction (Newton's 3rd law).

When you apply a force for a certain time, you impart an equal and opposite

** impulse, ** defined as: force, F x time, t to both the shuttle (or ball) and to yourself.

Then we also have F = ma (force = mass x acceleration, Newton's 2nd law). So the impulse, F x t = ma x t. Now acceleration x time is velocity, v. So Ft = mv.

But mv, mass x velocity, is

**momentum**.

So what happens is you give yourself and the ball, or shuttle,

** equal and opposite momentum.**
Because momentum is the product of mass and velocity, a 1kg mass with a velocity of 10m/sec has identical momentum to a mass of 10kg with a velocity of 1m/sec, or a mass of 100kg with a velocity of 0.1m/sec. And so on. So the ball, having less mass than you, moves away faster than you do, whereas the shuttle, being heavier, moves slower. But in all cases an equal and opposite momentum is given to the objects involved.